A common scenario I see play-out within the forums are people possibly extending their stove pipes within uninsulated areas within sub-zero climates, which causes stove pipe condensation to freeze.
Within sub-zero climates (areas where temperatures commonly go below zero), the stove (or flue) pipe can cause condensation or gases to freeze to the insides of double wall stainless steel insulated stove pipe.
When this scenario occurs, this highly combustible frozen creosote can reignite and cause a flash back or chimney fire down the stove pipe. More commonly, this causes a restriction for draft or combustion gases until it burns off. A very easy method for testing for this condition, stick a magnetic wood stove thermometer on the (uninsulated or insulated) stove pipe near the ceiling. During the coldest of Winter, you might start seeing some very hot temperatures if your stove pipe gases are cooling too quickly before they exit the top of the stack.
If you live within Alaska or Canada, I find it best to insulate the stove or flue pipe as far as you can, paying particularly close attention to uninsulated attic spaces, and try to not go further then one or two feet above an uninsulated space. (However, stacks need to also be above the peaks of the roof, or properly sized.)
Another solution commonly used within Alaska and Canada, removing the rain cap. Albeit, I hate doing this but anything above the flame causes restriction, causing gases to gather versus rapidly escape and further freezing at the rain cap and not just to the inside of the stove pipe.
I commonly see posts within the forum where people are complaining of leaks and other problems, and all follow-up comments seem to completely miss this dangerous scenario! Yes, you can burn a hot fire every so often, but with -40F to -60F, it is quite a futile effort at managing this scenario.
Within my garage where I installed an oil boiler, I ran the stack straight up through to the roof without any bends, and through an uninsulated attic space. Within the uninsulated attic space, I fabricated a four inch blue styrofoam (2 x 2" styrofoam boards) wall around the stack with the required spacing for mitigating any heat from the flue pipe. I also used a batt of Rock Wool for insulating just below the sheet metal roof, within the inside ceiling of this fabricated styrofoam walled structure around the flue pipe. The stake exits out the peak of the garage roof, about one to two feet above the peak. Now during the middle of Winter here with this particular install during weeks of -40F to -60F, I find I now have very little drips of icing at the top rain cap. I really just wish I would have insulated around my wood stove pipe within the house attic the same way several years ago when I was repairing the main house roof!
*NOTE: I usually find it's also best to usually go straight-up through the roof with the fewest bends as possible, as anything above a flame will cause pressure to build within the combustion chamber. (ie. Anything above a flame, will cause pressure within the combustion chamber to significantly increase, while also being exponentially more sensitive to negative pressures around the heating device.) And any bends or angles used in the flue or stove pipe will be areas where gases will build and/or possibly cause decreasing temperatures for combustion gas when compared to a straight up-through the roof installation.
**NOTE: Make sure there is adequate combustion air provided for the heating device being installed. Also note super cold air usually falls, and having a basement will allow cold air to fall into the basement during Winter. The same dynamics of pipe sizing and bends, tends to also apply to intake air. For my house intake combustion air, I also added a simple four inch 110v fan with a wall switch wired in the wall near the wood stove.
Hopefully those searching the Internet will come across this post, and find this very useful!
Within sub-zero climates (areas where temperatures commonly go below zero), the stove (or flue) pipe can cause condensation or gases to freeze to the insides of double wall stainless steel insulated stove pipe.
When this scenario occurs, this highly combustible frozen creosote can reignite and cause a flash back or chimney fire down the stove pipe. More commonly, this causes a restriction for draft or combustion gases until it burns off. A very easy method for testing for this condition, stick a magnetic wood stove thermometer on the (uninsulated or insulated) stove pipe near the ceiling. During the coldest of Winter, you might start seeing some very hot temperatures if your stove pipe gases are cooling too quickly before they exit the top of the stack.
If you live within Alaska or Canada, I find it best to insulate the stove or flue pipe as far as you can, paying particularly close attention to uninsulated attic spaces, and try to not go further then one or two feet above an uninsulated space. (However, stacks need to also be above the peaks of the roof, or properly sized.)
Another solution commonly used within Alaska and Canada, removing the rain cap. Albeit, I hate doing this but anything above the flame causes restriction, causing gases to gather versus rapidly escape and further freezing at the rain cap and not just to the inside of the stove pipe.
I commonly see posts within the forum where people are complaining of leaks and other problems, and all follow-up comments seem to completely miss this dangerous scenario! Yes, you can burn a hot fire every so often, but with -40F to -60F, it is quite a futile effort at managing this scenario.
Within my garage where I installed an oil boiler, I ran the stack straight up through to the roof without any bends, and through an uninsulated attic space. Within the uninsulated attic space, I fabricated a four inch blue styrofoam (2 x 2" styrofoam boards) wall around the stack with the required spacing for mitigating any heat from the flue pipe. I also used a batt of Rock Wool for insulating just below the sheet metal roof, within the inside ceiling of this fabricated styrofoam walled structure around the flue pipe. The stake exits out the peak of the garage roof, about one to two feet above the peak. Now during the middle of Winter here with this particular install during weeks of -40F to -60F, I find I now have very little drips of icing at the top rain cap. I really just wish I would have insulated around my wood stove pipe within the house attic the same way several years ago when I was repairing the main house roof!
*NOTE: I usually find it's also best to usually go straight-up through the roof with the fewest bends as possible, as anything above a flame will cause pressure to build within the combustion chamber. (ie. Anything above a flame, will cause pressure within the combustion chamber to significantly increase, while also being exponentially more sensitive to negative pressures around the heating device.) And any bends or angles used in the flue or stove pipe will be areas where gases will build and/or possibly cause decreasing temperatures for combustion gas when compared to a straight up-through the roof installation.
**NOTE: Make sure there is adequate combustion air provided for the heating device being installed. Also note super cold air usually falls, and having a basement will allow cold air to fall into the basement during Winter. The same dynamics of pipe sizing and bends, tends to also apply to intake air. For my house intake combustion air, I also added a simple four inch 110v fan with a wall switch wired in the wall near the wood stove.
Hopefully those searching the Internet will come across this post, and find this very useful!
